In an air conditioner system, the potential risk of the air conditioner includes the following aspects: excessively high compressor exhaust pressure may cause pipeline to burst, and thus erupted fragments and high pressure gas may spurt and hurt persons; and excessively high operating current of a compressor or a fan may result in excessively high temperature of the compressor or the fan, and thereby cause over-pressure of refrigerant or damage of the insulation. Components relating to the security are generally controlled by a control circuit. In order to avoid a security accident, a safety protection apparatus should be provided for the components, for example, a safety valve is provided for the compressor, or a protection circuit is provided for a control circuit of the compressor and the fan.
Electrical appliances are generally equipped with these safety protection apparatuses, but these safety protection apparatuses only provide a single protection. If a device of the safety apparatus malfunctions, the whole safety apparatus may malfunction and result in an accident. Since the safety protection apparatus only provides the single protection, the protection failures entirely once the safety protection apparatus is disabled.
In order to avoid the exhaust temperature/pressure from being too high, some of the conventional air conditioner safety circuits are equipped with exhaust temperature sensors, and some great power types of the circuits are further equipped with high pressure protection switches; however, in the safety circuits, physical parameters are only simply transmitted from a sensor to an microprocessor chip unit (MCU), and the protection is entirely realized by the software of the MCU. These type of safety protection circuits do not have a single-fault-tolerance design and a single-fault-tolerance ability. In addition, these sensors are directly connected to the MCU without a safety isolation circuit; and in order to save cost, a control circuit scheme in which the MCU is not isolated from the power supply is adopted in many air conditioner controllers; thus, the exhaust temperature sensor or the high pressure protection switch is not isolated from the power supply, and there is a risk of an electric shock and a potential security problem.
Hence, it is necessary to improve the conventional air conditioner protection apparatus, thereby realizing better protection for the air conditioner system.